• 한국정밀공학회지
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• 제11권4호
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• pp.158-164
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• 1994

A volumetric error compensation method was stueide with measuring systematic error of a Coordinate Measuring Machine(CMM). The volumetric error equations were proposed for a Moving Bridge type CMM. Using the error equations, error vectors in the measuring volume were corrected by a software method. The CMM was controlled by the compensation program separately in the measuring and moving function of the CMM proving. The linear accuracy of the CMM was measured by the Laser Interferometer and compared with the data before the volumetric error compensation. This method was proved as low cost and effective to reduce the systematic error of the CMM, as no hardware modification is required.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1368-1371
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• 1996

This paper presents an automatic calibration technique for piezoelectric low pressure transducer, which is useful to measure a pressure within 500 psi. This system with automatic calibration function and error correction algorithm generates standard dynamic pressure for the calibration of sensor. With the compensation for the offset voltage and the pressure error, the accuracy and the usefulness of the proposed scheme is validated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.1012-1016
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• 1996

This paper presents an automatic calibration technique for piezoelectic low pressure transducer, which is useful to measure a pressure within 500 psi. This system with automatic calibration function and error correction algorithm generates standard dynamic pressure for the calibration of sensor. With the compensation for the offset voltage and the pressure error, the accuracy and the usefulness of the proposed scheme is validated.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1991년도 학술발표회 논문집
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• pp.78-81
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• 1991

Digital radio data is composed of groups which are divided into 4 blocks of 26 bits. And each block is made up of information word and check word. Check word of digital radio data that is composed ofcode word and offset word is used for group/block synchronization and error correction. In this paper, we have investigated the group/block synchronizer using offext word and shortened cyclic decoder for correcting error produced during the radio data transimission. Also, we have simulated the decoding process of the proposed decoder. From the simulation results, we have confirmed that the proposed decoder most with the required coding capcbility.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.208-210
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• 1998

A high speed digital distance relaying algorithm based on a modified least square error method is proposed. To obtain stable phasor values very Quickly, first, a lowpass filter which has very short transient period and no overshoot is used. Secondly, the conventional least square error method is modified to the one having the data window of 3 samples by applying a FIR filter which removes the DC-offset component in current relaying signals.

• 한국정보통신학회논문지
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• 제17권2호
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• pp.294-301
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• 2013

OFDM 전송방식에서는 여러 개의 부반송파를 사용하여 데이터를 전송한다. 그러므로 송신 비선형 전력증폭기와 반송파 주파수편차에 의한 부반송파 간 간섭으로 인하여 수신기에서 비트 오류율이 증가된다. 무선 다중경로 페이딩 전송채널에서는 여러 개의 OFDM 부반송파 주파수 구간동안 연속적으로 전송이득이 작은 구간이 존재하므로, 전송 시 연집에러가 발생되어, 데이터 재생 시 비트 오류율이 증가 된다. 이러한 연집에러에 의한 비트 오류율의 감소에는 인터리버와 컨볼루션 에러제어코딩이 효과적이다. 한편 파일럿 심볼을 이용하여 전송채널을 추정하는 현 시스템에서는 전송채널 추정에러로 인하여 역시 비트 오류율이 증가된다. 그러므로 본 논문에서는 비선형 전력증폭기, 반송파 주파수편차 및 채널추정에러의 영향을 고려하여, 송신 신호가 다중경로 페이딩 채널을 통하여 전송될 때, 인터리버와 컨볼루션 코딩을 이용하는 OFDM 시스템의 데이터 비트 오류율 성능을 분석한다.

• 한국통신학회논문지
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• 제36권11C호
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• pp.641-648
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• 2011

주파수 영역 등화 기법은 다중 반송파 시스템의 대표적 특정으로 단일 탭의 채널 등화로 인한 낮은 구현 복잡도의 장점을 갖는다. SC-FDE (single carrier frequency domain equalization) 시스템은 단일 반송파 시스템에서 주파수 영역 등화 기법을 채택하고, 지연 확산에 대한 강점을 갖기 위해 CP(cyclic prefix)를 포함한 형태의 구조를 갖는다. 단일 반송파 시스템에서 동기 및 등화기를 거친 후 잔존하는, 공통 위상 오프셋 성분을 제거해야만 한다. 공통 위상 오프셋 성분은 송수신기 간 반송파 주파수 생성 시 발생하는 성분이기 때문에 이 오프셋이 큰 경우 성능 열화의 원인이 된다. 본 논문에서는 SC-FDE 시스템에서 공통 위상 오프셋 성분을 주파수 영역에서 보정하는 기법을 제안하였다. 동기 획득 및 등화를 위한 훈련 신호는 자기 상관관계 특성이 우수한 CAZAC (constant amplitude zero autocorrelation code) 시퀀스를 채택하였다. 제안한 공통 위상 오프셋 추적 성능은 컴퓨터 모의실험을 통해 평균 제곱 오차 (mean square error, MSE) 성능을 통해 확인하였고, 그 성능이 시간 영역에서 보정하는 것과 유사한 MSE 성능을 갖는 것을 확인하였다.

• Journal of Communications and Networks
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• 제8권2호
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• pp.234-240
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• 2006

We study the dynamic burst assembly based on traffic prediction and offset and delay differentiation in optical burst switching network. To improve existing burst assembly mechanism and build an adaptive flexible optical burst switching network, an approach called quality of service (QoS) based adaptive dynamic assembly (QADA) is proposed in this paper. QADA method takes into account current arrival traffic in prediction time adequately and performs adaptive dynamic assembly in limited burst assembly time (BAT) range. By the simulation of burst length error, the QADA method is proved better than the existing method and can achieve the small enough predictive error for real scenarios. Then the different dynamic ranges of BAT for four traffic classes are introduced to make delay differentiation. According to the limitation of BAT range, the burst assembly is classified into one-dimension limit and two-dimension limit. We draw a comparison between one-dimension and two-dimension limit with different prediction time under QoS based offset time and find that the one-dimensional approach offers better network performance, while the two-dimensional approach provides strict inter-class differentiation. Furthermore, the final simulation results in our network condition show that QADA can execute adaptive flexible burst assembly with dynamic BAT and achieve a latency reduction, delay fairness, and offset time QoS guarantee for different traffic classes.

• 한국통신학회논문지
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• 제34권4C호
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• pp.446-452
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• 2009

OFDM 시스템은 전송단자 수신단의 오실레이터의 불일치로 인해 발생하는 주파수 오프셋의 영향에 민감하다는 단점이 있다. 또한 주파수 오프셋은 ICI(Inter Carrier Interference) 문제를 발생시키고 부반송파 사이에 직교성을 왜곡한다. 본 논문에서는 ICI 영향을 분석하고, 기존의 SC 기법을 응용하여 새로운 알고리즘을 제안한다. 제안된 기법의 BER(Bit Error Rate)과 신호 품질을 결정짓는 CR(Carrier to Interference Ratio)을 분석하기 위하여 MATLAB 프로그램을 사용한다. 모의실험 결과, 주파수 오프셋이 0.3과 0.5 일 때 $10^{-3}$의 BER에서 BPSK 변조는 0.5dB, 1dB 이상, QPSK 변조는 1.6dB, 1.5dB 이상의 SNR 성능 향상을 보이며, CIR 성능도 최대 15dB 이상 향상 되었다. 결과적으로 제안한 기법이 기존의 기법보다 시스템 성능 향상에 효과적이다.

• Journal of Radiation Protection and Research
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• 제36권4호
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• pp.183-189
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• 2011

To quantitatively evaluate how setup errors in conjunction with dose gradients contribute to the error in IMRT dose quality assurance (DQA) measurements. The control group consisted of 5 DQA plans of which all individual field dose differences were less than ${\pm}5%$. On the contrary, the examination group was composed of 16 DQA plans where any individual field dose difference was larger than ${\pm}10%$ even though their total dose differences were less than ${\pm}5%$. The difference in 3D dose gradients between the two groups was estimated in a cube of $6{\times}6{\times}6\;mm^3$ centered at the verification point. Under the assumption that setup errors existed during the DQA measurements of the examination group, a three dimensional offset point inside the cube was sought out, where the individual field dose difference was minimized. The average dose gradients of the control group along the x, y, and z axes were 0.21, 0.20, and 0.15 $cGy{\cdot}mm^{-1}$, respectively, while those of the examination group were 0.64, 0.48, and 0.28 $cGy{\cdot}mm^{-1}$, respectively. All 16 plans of the examination group had their own 3D offset points in the cube. The individual field dose differences recalculated at the offset points were mostly diminished and thus the average values of total and individual field dose differences were reduced from 3.1% to 2.2% and 15.4% to 2.2%, respectively. The offset distribution turned out to be random in the 3D coordinate. This study provided the quantitative data that support the large individual field dose difference mainly stems from possible geometric errors (e.g., random setup errors) under the influence of steep dose gradients of IMRT field.